FIG. 5 shows an example of a known termination structure of a superconducting cable (see Patent Document 1). This termination structure is connected to a cable core 100 drawn from a terminal of a superconducting cable to communicate power between a low-temperature side and a room-temperature side. Specifically, the termination structure includes a superconductor 100a exposed from the core 100, a bushing 101 for providing electrical connection between the superconductor 100a and a conductor (not shown) disposed on the room-temperature side, a coolant vessel 102 accommodating a terminal of the bushing 101 on the low-temperature side and a connection part 110 connecting the superconductor 100a and the bushing, a vacuumed vessel 103 disposed so as to surround the coolant vessel 102, and a porcelain tube 104 protruding from the room-temperature side of the vacuumed vessel 103.
The bushing 101 includes a central conductive part 101a electrically connected to the superconductor 100a via the connection part 110 and a solid-state insulating layer 101b covering the conductive part 101a and formed of FRP. The bushing 101 is accommodated in the coolant vessel 102 and the porcelain tube 104. In this example, the superconductor 100a is connected to a connection conductor 120 formed of a normal conductor material such as copper. The connection conductor 120 is connected to the conductive part 101a of the bushing 101 via the connection part 110. The bushing 101 has flanges 101c and 101d around the periphery thereof. The bushing 101 is fixed to the coolant vessel 102 with the flange 101c and to the vacuumed vessel 103 with the flange 101d. 
The coolant vessel 102 is filled with a liquid coolant, such as liquid nitrogen, to cool the bushing 101, the connection part 110, and the connection conductor 120. The vacuumed vessel 103 includes a cylindrical intermediate vacuum part 103a connecting the coolant vessel 102 on the low-temperature side and the porcelain tube 104 on the room-temperature side. The bushing 101 is inserted into the intermediate vacuum part 103a to reduce heat penetration from the room-temperature side to the low-temperature side. That is, part of the vacuumed vessel 103 has a double structure including both the intermediate vacuum part 103a and an outer vacuum part 103b. The porcelain tube 104 is filled with an insulation fluid such as insulation oil or SF6 gas.
Patent Document 1: Japanese Unexamined Patent Application Publication No. 2002-238144